April 26, 2010 (Anaheim, Calif.) -- Vitamin D, already considered a way to
help fight colds, cancer, diabetes, heart disease, and other ills, may also
keep people mobile in their golden years, according to a new study.

"Those with better vitamin D levels started out better and ended up better
on physical performance tests," she tells WebMD.

Vitamin D in Older Adults: Study Details

Results have been mixed in previous studies looking at whether vitamin D
helps physical functioning in older adults, Houston says. Some studies found no
effect of boosting low vitamin D levels in seniors and other studies showed an
association.

Vitamin D, important for promoting calcium absorption, maintaining muscle
strength, promoting bone growth and repair, and other activities, is produced
when ultraviolet rays from the sun strike the skin and spark its synthesis.

It's found naturally in few foods and is added to others. Deficiency is
common, especially with age, because the ability to synthesize vitamin D
declines. Older adults also have difficulty converting vitamin D to its active
hormone form.

In the new study, researchers wanted to see if vitamin D could delay
age-related changes in physical functioning.

So Houston and her colleagues evaluated 2,641 older men and women, on
average age 75.

The older adults were part of the Health, Aging, and Body Composition
(Health ABC) Study that looked at the links between body composition, health
conditions, and mobility with age.

For this new analysis, Houston divided the adults into three groups,
depending on whether their vitamin D levels as evaluated from blood samples was
low, medium, or high.

Those terms were relative, she tells WebMD, as "two-thirds had vitamin D
insufficiency."

For the study, low blood levels of vitamin D were under 50 nanomoles per
liter (nmol/L), high blood levels were those 75 or higher, and levels of 50-75
were intermediate.

All the adults were tested to assess physical function, including walking
400 meters (about 1/4 mile) as fast as possible, standing from a chair without
using the arms, balance tasks, and other tests of their lower extremity
strength and functioning.

The tests were given at the start of the study and repeated two and four
years later.

Vitamin D Levels and Physical Functioning

"Over time, everybody declined in the tasks, as expected," Houston says.

However, those who started out with higher vitamin D did better on the tests
than those whose vitamin D levels were lower at the start. "People who had
higher levels started out with better physical functioning and because they
started out better, they remained at higher physical functioning," Houston
says.

"Those with adequate or optimal vitamin D status [the highest group] had
approximately 5% higher physical performance scores and 5% faster walk speed on
the 400-meter walk compared to those with insufficient vitamin D status at the
4-year follow up," she says.

Vitamin D Levels and Mobility: Second View

The study results aren't surprising to Erica T. Goode, MD, MPH, a physician
at the California Pacific Medical Center's Health & Healing Center-Clinic
in San Francisco, who was attending the meeting.

"I'm sure that this is accurate," she says of the finding that those adults
with higher vitamin D levels performed better on the physical functioning
tests.

Vitamin D: How Much Is Enough?

Exactly how much vitamin D is enough for older adults (and others, as well)
is a matter of ongoing debate.

According to the Institute of Medicine, an adequate intake is 400
international units (IU) for adults 51 to 70 and 600 IU for people older than
70. A level of 2,000 IU is considered the "upper tolerable limit" by the
IOM.

But some nutrition scientists have challenged those recommendations,
contending that up to 10,000 IU a day of the vitamin is generally safe.

"By all means, try to get at least 1,000 IU," Goode says.

The IOM is reviewing the data and is expected to have an update in May
2010.